Tips from PC World

• Choose the right format. The file types that will still be readable far into the future are the most popular and widely used ones. So choose industry-standard formats that many programs support, such as JPEG for photos or MP3 for music, rather than proprietary or lesser-known formats like PSD (Photoshop) for pictures or FLAC for audio files.
• Use write-once discs. Go with CD-R or DVD-R/DVD+R; stay away from RW media. You don't want to accidentally write over data meant for long-term archiving, and -RW media is not as stable as write-once media. Also look for discs labeled as "Archival" and "Scratch-Resistant." These are manufactured to higher standards, and use special coatings and more stable reflective layers.
• Make multiple copies and store them properly. Store multiple copies of your data in different locations, such as your home, your safe deposit box, and with a trusted relative or two. Keep them in a cool, dry place away from sunlight. Heat, moisture and UV rays are the most damaging things you can expose your discs to.
• Check them regularly. Each time you get a new computer, make it a habit to pop in your archived discs and make sure you can still read them. If not, convert them using your old computer before you dispose of it.